Plasma beta-endorphin and stress hormones in stress and adaptation

The experiments on white rats have shown that the induction of 4 hour stress produces an acute increase in beta-endorphin level, as well as characteristic changes in ACTH, cortisol, insulin, thyroxin and triiodothyronine concentrations. Different types of adaptation (training with short stress periods or injection of rhodiola rosea extract) promote a moderate increase in the amount of serum immunoreactive beta-endorphin, preventing its subsequent stress-induced elevation. Adaptation is characterized by a decrease or total prevention of hormonal changes peculiar to stress. The role of opioid neuropeptides in enhancing stress tolerance and the effect of adaptation factors are discussed.     

Oxidative stress markers in patients with post-traumatic stress disorder

Recent study data support the role of oxidative stress in diverse psychiatric disorders. Oxidative stress results from an oxidant/antioxidant imbalance, an excess of oxidants and/or a depletion of antioxidants. There are numerous studies that indicate that free radicals (FRs) damage neurons, and then play an important role in the pathophysiology of schizophrenia and depression. Active oxygen can cause considerable damage and disrupt the important physiological functions of proteins, lipids, enzymes and DNA. The aim of our study was to investigate the possible differences in the concentration of tromboxane B2, 8-OHdG and protein carbonyls, as significant markers of oxidative damage, and urate, albumin and total protein concentrations as antioxidative molecules in PTSD patients in comparison to the healthy control group. The study included 74 male participants who were active soldiers in the Croatian armed forces from 1991 to 1995. 46 subjects with chronic and current PTSD were recruited from the Department of Psychiatry of Dubrava University Hospital during 2010, 28 healthy subjects were recruited in the same period during the regular medical examination at the Dubrava University Hospital. Study results have shown that there is no statistically significant difference in urinary concentrations of 8-OHdG, serum thromboxane B2, and serum urates between two studied groups. Statistically significant difference of the protein carbonyl concentrations was examined. Concentrations were significantly lower in the PTSD group than in the control group. The clinical significance of these results was examined using ROC analysis. The obtained ROC curves did not separate the groups in a satisfactory manner.     

Acute heat stress induces oxidative stress in broiler chickens

The stress responses and possible oxidative damage in plasma, liver and heart were investigated in broiler chickens acutely exposed to high temperature. Eighty 5-week old broiler chickens were exposed to 32 degrees C for 6h. The extent of lipid peroxidation, activities of superoxide dismutase and total antioxidant power in plasma, liver and heart tissues were investigated. Meanwhile, the blood metabolites such as glucose, urate, triiodothyronine, thyroxine, corticosterone, ceruloplasmin and creatine kinase were measured before and after 3 and 6h of heat exposure. The results showed that oxidative stress could be induced in 5-week old broiler chickens by acute heat exposure (32 degrees C, 6h). The results suggest that the elevated body temperature can induce the metabolic changes that are involved in the induction of oxidative stress. The liver is more susceptible to oxidative stress than heart during acute heat exposure in broiler chickens. The oxidative stress should be considered as part of the stress response of broiler chickens to heat exposure.     

Oxidative stress and cellular stress response in diabetic nephropathy

Oxidative stress has been suggested to play a main role in the pathogenesis of type 2 diabetes mellitus and its complications. As a consequence of this increased oxidative status, a cellular-adaptive response occurs requiring functional chaperones, antioxidant production, and protein degradation. This study was designed to evaluate systemic oxidative stress and cellular stress response in patients suffering from type 2 diabetes-induced nephropathy and in age-matched healthy subjects. Systemic oxidative stress has been evaluated by measuring advanced glycation end-products (pentosidine), protein oxidation (protein carbonyls [DNPH]), and lipid oxidation (4-hydroxy-2-nonenal [HNE] and F2-isoprostanes) in plasma, lymphocytes, and urine, whereas the lymphocyte levels of the heat shock proteins (Hsps) heme oxygenase-1 (HO-1), Hsp70, and Hsp60 as well as thioredoxin reductase-1 (TrxR-1) have been measured to evaluate the systemic cellular stress response. We found increased levels of pentosidine (P < 0.01), DNPH (P < 0.05 and P < 0.01), HNE (P < 0.05 and P < 0.01), and F2-isoprostanes (P < 0.01) in all the samples from type 2 diabetic patients with nephropathy with respect to control group. This was paralleled by a significant induction of cellular HO-1, Hsp60, Hsp70, and TrxR-1 (P < 0.05 and P < 0.01). A significant upregulation of both HO-1 and Hsp70 has been detected also in lymphocytes from type 2 diabetic patients without uraemia. Significant positive correlations between DNPH and Hsp60, as well as between the degree of renal failure and HO-1 or Hsp70, also have been found in diabetic uremic subjects. In conclusion, patients affected by type 2 diabetes complicated with nephropathy are under condition of systemic oxidative stress, and the induction of Hsp and TrxR-1 is a maintained response in counteracting the intracellular pro-oxidant status.     

Sources of stress in captivity

Animals housed in artificial habitats are confronted by a wide range of potentially provocative environmental challenges. In this article, we review many of the potential stressors that may adversely affect animals living in captivity. These include abiotic, environmental sources of stress such as artificial lighting, exposure to loud or aversive sound, arousing odors, and uncomfortable temperatures or substrates. In addition, confinement-specific stressors such as restricted movement, reduced retreat space, forced proximity to humans, reduced feeding opportunities, maintenance in abnormal social groups, and other restrictions of behavioral opportunity are considered. Research in support of the claims for these environmental elements as stressors for captive animals reveals no unique suite of behavioral or physiological responses that will clearly indicate the cause of those responses; rather, it is up to us as managers and caretakers of animals in captivity to evaluate enclosures and husbandry practices to ensure the optimal well-being of animals in our care.     

Purine stress in crithidia: adaptation of a parasite to environmental stress

How parasitic protozoa survive varying nutrient levels is a key issue in parasitology. Here, Annette Gero explains how the Trypanosomatid Crithidia luciliae responds to purine stress by increasing the rates of transport of nucleosides and bases from the environment and by increasing the activity of the ectoenzyme 3'-nucleotidase (3'NTase), which breaks down external nucleotides so that they can be salvaged as nucleosides. The increase in activity of the purine transporters, and the 3'NTase activity is simultaneous with a general increase in the purine metabolic pathway, hence ensuring that purines are readily available to the parasite during purine stress.     

Shear stress modulates RAGE-mediated inflammation in a model of diabetes-induced metabolic stress

Atherosclerosis occurs preferentially at sites of disturbed blood flow despite the influence of risk factors contributing to systemic inflammation. The receptor for advanced glycation endproducts (RAGE) is a prominent mediator of inflammation in diabetes that is upregulated in atherosclerotic plaques. Our goal was to elucidate a role for arterial hemodynamics in the regulation of RAGE expression and activity. Endothelial RAGE expression was elevated at sites of flow disturbance in the aortas of healthy swine. To demonstrate a direct role for physiological shear stress (SS) in modulating RAGE expression, human aortic endothelial cells (HAEC) were exposed to high SS (HSS; 15 dyn/cm(2)), which downregulated RAGE by fourfold, or oscillatory SS (OSS; 0 ± 5 dyn/cm(2)), which upregulated RAGE by threefold, compared with static culture at 4 h. In a model of diabetes-induced metabolic stress, HAEC were chronically conditioned under high glucose (25 mM) and then simultaneously stimulated with TNF-α (0.5 ng/ml) and the RAGE ligand high mobility group box 1 (HMGB1). A 50% increase in VCAM-1 expression over TNF-α was associated with increased cytoplasmic and mitochondrial reactive oxygen species and NF-κB activity. This increase was RAGE-specific and NADPH oxidase dependent. In activated HAEC, OSS amplified HMGB1-induced VCAM-1 (3-fold) and RAGE (1.6-fold) expression and proportionally enhanced monocyte adhesion to HAEC in a RAGE-dependent manner, while HSS mitigated these increases to the level of TNF-α alone. We demonstrate that SS plays a fundamental role in regulating RAGE expression and inflammatory responses in the endothelium. These findings may provide mechanistic insight into how diabetes accelerates the nonrandom distribution of atherosclerosis in arteries.     

Uniform stress state in bone structure with residual stress.

Residual stress and strain in living tissues have been investigated from the viewpoint of mechanical optimality maintained by adaptive remodeling. In this study, the residual stresses in the cortical-cancellous bone complex of bovine coccygeal vertebrae were examined. Biaxial strain gages were bonded onto the cortical surface, so that the gage axes were aligned in the cephalocaudal and circumferential directions. Strains induced by removal of the end-plate and the cancellous bone were recorded sequentially. The results revealed the existence of compressive residual stress in the cortical bone and tensile residual stress in the cancellous bone in both the cephalocaudal and the circumferential direction. The observed strains were examined on the basis of the uniform stress hypothesis using a three-bar model for the cephalocaudal direction and a three-layered cylinder model for the circumferential direction. In this model study, the magnitude of effective stresses, which is defined as the macroscopic stress divided by the area fraction of bone material, was found not to differ significantly between cephalocaudal and circumferential directions, although they were evaluated using independent models. These results demonstrate that the uniform stress state of the cortical-cancellous bone structure is consistent with results obtained in the cutting experiment when the existence of residual stress is taken into account.     

Disulfide stress: a novel type of oxidative stress in acute pancreatitis

Glutathione oxidation and protein glutathionylation are considered hallmarks of oxidative stress in cells because they reflect thiol redox status in proteins. Our aims were to analyze the redox status of thiols and to identify mixed disulfides and targets of redox signaling in pancreas in experimental acute pancreatitis as a model of acute inflammation associated with glutathione depletion. Glutathione depletion in pancreas in acute pancreatitis is not associated with any increase in oxidized glutathione levels or protein glutathionylation. Cystine and homocystine levels as well as protein cysteinylation and γ-glutamyl cysteinylation markedly rose in pancreas after induction of pancreatitis. Protein cysteinylation was undetectable in pancreas under basal conditions. Targets of disulfide stress were identified by Western blotting, diagonal electrophoresis, and proteomic methods. Cysteinylated albumin was detected. Redox-sensitive PP2A and tyrosine protein phosphatase activities diminished in pancreatitis and this loss was abrogated by N-acetylcysteine. According to our findings, disulfide stress may be considered a specific type of oxidative stress in acute inflammation associated with protein cysteinylation and γ-glutamylcysteinylation and oxidation of the pair cysteine/cystine, but without glutathione oxidation or changes in protein glutathionylation. Two types of targets of disulfide stress were identified: redox buffers, such as ribonuclease inhibitor or albumin, and redox-signaling thiols, which include thioredoxin 1, APE1/Ref1, Keap1, tyrosine and serine/threonine phosphatases, and protein disulfide isomerase. These targets exhibit great relevance in DNA repair, cell proliferation, apoptosis, endoplasmic reticulum stress, and inflammatory response. Disulfide stress would be a specific mechanism of redox signaling independent of glutathione redox status involved in inflammation.     

Oxidative stress in cyanobacteria

Reactive oxygen species (ROS) are byproducts of aerobic metabolism and potent agents that cause oxidative damage. In oxygenic photosynthetic organisms such as cyanobacteria, ROS are inevitably generated by photosynthetic electron transport, especially when the intensity of light-driven electron transport outpaces the rate of electron consumption during CO₂ fixation. Because cyanobacteria in their natural habitat are often exposed to changing external conditions, such as drastic fluctuations of light intensities, their ability to perceive ROS and to rapidly initiate antioxidant defences is crucial for their survival. This review summarizes recent findings and outlines important perspectives in this field.     

Nitrosative stress in plants

Nitrosative stress has become a usual term in the physiology of nitric oxide in mammalian systems. However, in plants there is much less information on this type of stress. Using olive leaves as experimental model, the effect of salinity on the potential induction of nitrosative stress was studied. The enzymatic l-arginine-dependent production of nitric oxide (NOS activity) was measured by ozone chemiluminiscence. The specific activity of NOS in olive leaves was 0.280nmol NOmg(-1) proteinmin(-1), and was dependent on l-arginine, NADPH and calcium. Salt stress (200mM NaCl) caused an increase of the l-arginine-dependent production of nitric oxide (NO), total S-nitrosothiols (RSNO) and number of proteins that underwent tyrosine nitration. Confocal laser scanning microscopy analysis using either specific fluorescent probes for NO and RSNO or antibodies to S-nitrosoglutathione and 3-nitrotyrosine, showed also a general increase of these reactive nitrogen species (RNS) mainly in the vascular tissue. Taken together, these findings show that in olive leaves salinity induces nitrosative stress, and vascular tissues could play an important role in the redistribution of NO-derived molecules during nitrosative stress.     

Oxidative stress in haemostasis

The normal hemostatic mechanisms consist of a balance between hemorrhage and thrombosis that is achieved through the interaction of the blood vessels, blood platelets, the coagulation and fibrinolytic factors. The vascular endothelium sustains the balance between prevention and stimulation of platelet activation, thrombogenesis and fibrinolysis and between vasoconstriction and vasodilatation. Endothelial dysfunction associated with different cardiovascular diseases is related to the local formation of reactive oxygen/nitrogen species, mainly peroxynitrite that is produced in a rapid reaction between nitric oxide and superoxide anion. Reactive oxygen/nitrogen species induce changes in the structure and function in hemostatic elements. Proteins and lipids are major initial targets in endothelial cells, blood platelets and plasma. Reaction of reactive oxygen species and nitrogen species, including peroxynitrite, with cellular proteins can lead to nitration of aromatic amino acid residues, oxidation of thiol groups and conversion of some amino acid residues into carbonyl derivative. Oxidative/nitrative modifications of platelet proteins may induce changes of their signaling and haemostatic function (activation). Peroxynitrite also causes oxidation and nitration of fibrinogen--a key protein in coagulation cascade and plasminogen (the main protein of fibrinolysisprocess) changing their hemostatic functions. Oxidative/nitrative modifications of different components of haemostasis system have been observed in several cardiovascular diseases.     

Photooxidative stress in plants

The light-dependent generation of active oxygen species is termed photooxidative stress. This can occur in two ways: (1) the donation of energy or electrons directly to oxygen as a result of photosynthetic activity; (2) exposure of tissues to ultraviolet irradiation. The light-dependent destruction of catalase compounds the problem. Although generally detrimental to metabolism, superoxide and hydrogen peroxide may serve useful functions if rigorously controlled and compartmentalised. During photosynthesis the formation of active oxygen species is minimised by a number of complex and refined regulatory mechanisms. When produced, active oxygen species are eliminated rapidly by efficient antioxidative systems. The chloroplast is able to use the production and destruction of hydrogen peroxide to regulate the thermal dissipation of excess excitation energy. This is an intrinsic feature of the regulation of photosynthetic electron transport. Photoinhibition and photooxidation only usually occur when plants are exposed to stress. Active oxygen species are part of the alarm-signalling processes in plants. These serve to modify metabolism and gene expression so that the plant can respond to adverse environmental conditions, invading organisms and ultraviolet irradiation. The capacity of the antioxidative defense system is often increased at such times but if the response is not sufficient, radical production will exceed scavenging and ultimately lead to the disruption of metabolism. Oxidative damage arises in high light principally when the latter is in synergy with additional stress factors such as chilling temperatures or pollution. Environmental stress can modify the photooxidative processes in various ways ranging from direct involvement in light-induced free radical formation to the inhibition of metabolism that renders previously optimal light levels excessive. It is in just such situations that the capacity for the production of active oxygen species can exceed that for scavenging by the antioxidative defense systems. The advent of plant transformation, however, may have placed within our grasp the possibility of engineering greater stress tolerance in plants by enhancement of the antioxidative defence system.     

Oxidative stress in plants

Oxidative stress, defined as a shift of the balance between prooxidative and antioxidative reactions in favor of the former seems to be a common denominator of the action of various agents on living organisms. This review briefly presents the sources of reactive oxygen species and means of antioxidative defense in plants, means of assessment of oxidative stress and exemplary data on the induction of oxidative stress by various environmental and biological factors such as hyperoxia, light, drought, high salinity, cold, metal ions, pollutants, xenobiotics, toxins, reoxygenation after anoxia, experimental manipulations, pathogen infection and aging of plant organs.     

Oxidative stress in mice

The aim of this study was to analyze the effect of high dietary Fe on liver antioxidant status in mice fed a corn-oil-enriched diet. Male Balb/c mice were fed for 3 wk with a standard diet enriched with 5% by weight of corn oil with adequate Fe (FCO diet) or supplemented with 1% carbonyl Fe (FCOFe diet). The control group was fed a standard diet. The high-Fe diet induced a twofold increase of hepatic Fe level. However, an increase of thymic Fe level has been induced solely by dietary fat. The hepatic copper (Cu) level slightly decreased in the FCO diet. In the spleen, the high-Fe diet-induced increase of Fe level was negatively correlated with the Cu level. The antioxidant status was influenced by both dietary fat and Fe. Mice fed corn-oil-enriched diets had a higher concentration of thiobarbituric acid-reactive substances (TBARS), with a greater increase in the FCOFe diet. Fatty acid analysis showed decreased n−3 and n−6/n−3 ratio, particularly in the FCOFe diet. Hepatic Cu/Zn superoxide dismutase (CuZn-SOD) activity was decreased in FCO diet, and Fe supplementation caused a further decrease in the enzyme activity. These results suggest that feeding with corn oil-enriched diet increases oxidative damage by decreasing antioxidant enzyme defense. The high-Fe diet additionally affects the antioxidant defense system, further increasing the tissue's susceptibility to lipid peroxidation. Additionally, both corn-oil- and Fe-enriched diets have increased the Cu requirement in mice.